DESCRIPTION OF THE PRIOR ART
It is known that carbon monoxide can be oxidized to carbon dioxide and that sulfur dioxide can be oxidized to sulfur trioxide by contact, in dilute concentrations in air, with an oxidation catalyst containing palladium (II) and copper (II) halide salts in a solution or on a substrate or support such as alumina. Such catalysts are described in considerable detail in U.S. Pat. No. 3,790,662, issued Feb. 5, 1974, to Larox Research Corporation for "Palladium Compositions Suitable As Oxidation Catalysts", in U.S. Pat. No. 3,849,336, issued Nov. 19, 1974, to Larox Research Corporation for "Palladium Compositions Suitable As Oxidation Catalyst", and in copending application of Victor F. Zackay and Donald R. Rowe, Ser. No. 504,517 filed June 15, 1983 for "Improved Palladium Catalyst". The disclosures of these patents and application are incorporated herein and made a part of this specification by this reference.
Two major sources of pollution are cigarette smoke and automobile exhaust. Both of these sources produce gaseous pollutants which include hydrogen sulfide and hydrogen cyanide. These compositions are notable irritants even in dilute concentrations in air at normal or ambient temperatures which range generally from about -20.degree. C. to about 50.degree. C. Gaseous pollutants such as hydrogen sulfide and hydrogen cyanide are present in cigarette smoke at irritant levels, and in closed or confined areas, gases such as hydrogen cyanide can be present at levels which could be life threatening. Hydrogen cyanide is, in terms of toxicological impact, probably the most critical component of cigarette smoke next to carbon monoxide. Hydrogen sulfide occurs at a highly irritant level in smoke. Research has determined that hydrogen sulfide can be present in cigarette smoke in amounts as low as 40 parts per million and as high as 160 parts per million. Hydrogen cyanide has been discovered at concentrations as low as 25 parts per million and as high as 1,000 parts per million. "Smoking and Health" U.S. Public Health Service Publication No. 1103 , Department of Health, Education and Welfare, Washington, D.C., 1964; "Smoking and Health" report of the Surgeon General of the United States, U.S. Public Health Service, 1979; "Smoking and Health" W. H. Griest et al., Oakridge National Laboratory Report ORNL/TM-6144/PL, 1977; and "Smoking and Health" A. D. Horton et al., J. Chromatography, 90, 63-70 (1974). Heretofore there has been no known way to remove hydrogen sulfide and hydrogen cyanide in low concentrations from air at ambient temperatures other than by the use of wet alkaline scrubbers.